Tuy nhiên Canon đang test công nghệ mới, không biết khi nào ra mắt.
<h3>Low ISO Dynamic Range and Canon</h3> At present, Canon cameras
underperform on the Dynamic Range test or, more precisely, on dynamic range measured at
low ISO settings. At high ISO, the Canon 1Dx actually has a
better dynamic range than the D800(E), and the Canon 5D3 matches the D800(E) at high ISO. This confirms that newer Canon models like the 5D3 and the 1Dx are state-of-the-art as high ISO cameras.
But the problem with Canon (and all tested sensors except those with the latest and greatest Sony sensors) is that the dynamic range hardly increases when you go below about 800 ISO. This is consistent with test photos that show that the 5D3 cannot match the low ISO clean shadow performance of the D800(E), the K-5(II/IIs) or the D7000.
This is illustrated in Photo 2 that shows a 750x750 pixel crop of a 21 MPixel wedding
[53] photo taken at 200 ISO on a Canon 5D Mark III. The top of the image is exposed at 100%
[54], while the bottom contains 0.05% gray
[55]. This implies an estimated dynamic range of 2000:1 or 11 EV. DxOMark’s more precise measurement gives 11.65 EV of dynamic range for the Canon 5D3 at the 200 ISO setting.
Note that the noise at the bottom of Photo 2 exhibits horizontal “banding”. As the camera was held in portrait mode, this is normally called
vertical banding or “fixed-pattern column noise”. If you cannot see this (or details in the other photos) be sure you are viewing this on a calibrated monitor. And you may want to save the picture and inspect it in a trustworthy photo viewing application such as Photoshop, Lightroom or Capture One.
Sony claims
[56] that they are the first and only sensor supplier so far that is able to avoid visible fixed pattern (column) noise. For this, Sony uses a combination of having on-chip analog to digital convertors (one ADC per column
[57]) and a digital trick to elegantly subtract the black or empty level of each sensor pixel. In our rain & cups analogy, it is like emptying the cup before starting the measurement, first weighing it (with any residual water inside), then exposing the cup to rain, and then weighing the cup a second time. Subtracting the original weight avoids measurement errors due to the “empty” weight and due to measurement offsets. In sensor engineering, this technique is known as Correlated Double Sampling and is standard for both digital weighing
[58] and for light sensors, but Sony has a somewhat cooler way to do this.
Canon users frequently wonder whether Canon will catch up, particularly in terms of low ISO dynamic range – given that it has lost the lead since the Nikon D3x back in late 2008.
Some industry analysts[59] expect that Canon will catch up when they start using a new state-of-the-art 0.2 μm copper[60] sensor manufacturing process which they are currently testing. This allows Canon to switch from off-chip analog to digital converters to on-chip per-column ADCs.
